1. Field of the Invention
The present invention relates to a manufacturing method for a stacked wafer configured by bonding a mother wafer having a plurality of first semiconductor devices and a stacking wafer having a plurality of second semiconductor devices in such a manner that electrodes provided on the front side of each second semiconductor device are respectively bonded to electrodes provided on the front side of each first semiconductor device.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines called streets are formed on the front side of a substantially disk-shaped semiconductor wafer to partition a plurality of regions where a plurality of semiconductor devices such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along the streets to thereby divide the regions where the semiconductor devices are formed from each other, thus manufacturing the individual semiconductor devices.
For the purposes of size reduction and higher functionality of equipment, a module structure having the following configuration is in practical use. This module structure is such that a plurality of second semiconductor devices (stacking devices) are stacked on the front side of a mother wafer having a plurality of first semiconductor devices and that electrodes of each second semiconductor device are respectively connected to electrodes of each first semiconductor device formed on the front side of the mother wafer (see Japanese Patent Laid-open No. 2003-249620, for example). This packaging technique eliminates the need for wires for connecting the electrodes provided on the front side of each first semiconductor device to the electrodes provided on the front side of each second semiconductor device. That is, a wire bonding step can be omitted to thereby improve the productivity.
For the purposes of size reduction and higher functionality of equipment produced by using such a stacked wafer, the back side of a stacking wafer having the plural second semiconductor devices is ground to reduce the thickness of the stacking wafer to tens of micrometers before it is stacked on the front side of the mother wafer. However, when the stacking wafer is ground to tens of micrometers in thickness, the stacking wafer loses its rigidity like a sheet of paper, so that it bends. Accordingly, it is difficult to stack the stacking wafer on the mother wafer so that the second semiconductor devices respectively correspond to the first semiconductor devices in proper positions, thus causing faulty electrical continuity between the electrodes of each second semiconductor device and the electrodes of the corresponding first semiconductor device.
To prevent the bending of a wafer due to grinding, there has been proposed a method of grinding the back side of the wafer in the condition where a substrate formed from a hard plate is bonded through a wax or the like to the front side of the wafer (see Japanese Patent Laid-open No. 2004-207606, for example).